UPDATE 1-French energy union to strike over site closures

* Thermal, nuclear power output to be hit

* EDF says will have estimated impact on Tuesday

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PARIS, Oct 8 (Reuters) - France's CGT trade union has calledfor a 24-hour strike in the energy sector to protest againstsite closures, an action that could hit power production at thecountry's thermal and nuclear plants.

The strike is set to start at 1900 GMT on Monday, a CGTspokesman said. The action is part of Tuesday's national day ofprotest against job cuts and plant closures called by CGT,France's biggest trade union.

"In thermal power stations, we will be at zero(production)," CGT spokesman Laurent Langlard told Reuters. "Weare also expecting production reductions in nuclear power."

It was not clear by how much production could be cut. Frenchgrid operator RTE was not immediately available for comment.

A spokeswoman for EDF , France's biggest powercompany said it had received the strike notice by CGT but thatit will only be able to provide an estimate for its impact fromTuesday, around 0900 GMT.

The strike comes after President Francois Hollande said hewould close France's oldest nuclear power station at Fessenheimnear the German border in 2016.

"With the closure of Fessenheim, we are left wondering. Wewere told it was the oldest nuclear power station, but there isalways an oldest one. So which one will be next?" Langlard said.

German power group E.ON also announced last yearthat it would close four out of seven coal plants that itoperates in France. It also has two gas-powered plants in thecountry.

E.ON's coal and gas plants in France have a combinedelectricity capacity of 3,000 megawatts, equivalent to aboutthree nuclear reactors.

(Reporting by Michel Rose; Editing by David Goodman)


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